Here is an interesting chart regarding Android device updates.http://theunderstatement.com/post/11982112928/android-orphans-visualizing-a-sad-history-of-support
Most Android devices just don't get updates and worse, phones like the Samsung Behold II already 2 major updates behind when they are released. Outside of super-nerds, people who buy Android phones JUST DON'T CARE about their phone OS, because to them it is just that, a phone. It makes calls and sends SMS and MMS messages. It even has the weather! But many of these 500k activations a week are on phones so crippled by vendors that they barely escape the 'feature phone' classification.
Android has huge adoption numbers, but so did Symbian phones 5 years ago. No one was getting all excited about that platform. It was a utility. A thing that was cheap for hardware manufacturers to slap on to their junky plastic phones.
Android, for all the excitement it riles up in tech pundits (who, lets face it, don't represent real people), is a commodity OS that does not engage users. Which is fine. After all, they're just phones.